1. Field of the Invention
The present invention relates to piezoelectric devices and manufacturing method thereof, wherein one of a lid, a base, and an adhesive agent of the piezoelectric device is colored.
2. Description of the Related Art
A piezoelectric device is known to have a piezoelectric vibrating piece, disposed in a cavity formed by two glass plates or crystal plates, and vibrates when voltage is applied. The cavity in the piezoelectric device is sealed and formed by bonding the two glass plates or crystal plates to each other with an adhesive agent. The hermetic seal of the cavity is impaired due to the defective bonding of the glass plates or crystal plates. Consequently, such piezoelectric devices become an inferior product. From the aspect of product quality management, the inspection of inferior products is preferably carried out either during the manufacturing process of the piezoelectric devices or after completing the production. Because the glass plates and crystal plates are highly transparent, the bonding part of the adhesive agent can be observed to confirm defect in the bonding portion directly after forming the cavity. However, because of the high transparency, various lights may pass through the glass plates or crystal plates. As a result, it is difficult to clearly observe and identify the bonding defect.
In terms of identifying inferior products, for example, Patent Reference 1 discloses an inspection method. The method utilizes the difference in optical transmittance to inspect the quality products and the inferior products of lid stock used for sealing electronic parts. According to this inspection method, the difference between the optical transmittances of the quality products and the inferior products is enhanced by coloring the adhesive agent formed in the lid stock used for sealing the electronic part, so as to find out the inferior products.